WCF/WF - add json type input parameter in Request body of REST WCF

to add/pass json  type input parameter in Request body of REST WCF.

The input json type will be having around 40 fields,

Also this json type parameter comes via Xcode,Objective C Apps i.e, this Rest WCF will be consumed in apple mobile app.This json type needs to  stored in database table.

via REST Client addon , we're unable to add Json type parameter in request body to check the working of service.

But the service added as service reference in asp.net application works also works when testing with WCF Client.

kindly advise.